Explain to children that long ago, the sun had a very important job: It was the only way people were able to tell time! They used the shadows the sun made on a device called a sundial to keep track of time. Then try this experiment to let children see how sundials work.

Fill an empty coffee can with wet sand. Stick a ruler in the middle of the sand.

Find a sunny spot on blacktop or sidewalk where you can draw with chalk. Make sure the spot is in open sunlight so that other shadows don't interfere.

Place the can on the sidewalk and look for the line of the ruler's shadow. Trace over the line with chalk.

Go out again in an hour or two and find the ruler's shadow. Again, trace the line with chalk. Continue checking and tracing every hour or two throughout the day. In what direction are the lines moving? How far apart are they? Compare the lines to those on the clock in your classroom. You just might see a similarity!